Delay compositions for delay electric detonators



Thomas Z. Ball, New Ringgold, and William D. Trevorrow, Tamaqua, Pa., assignors to Atlas Chemical Industries, Inc., Wilmington, Del., a corporation of Delaware No Drawing. Filed Oct. 24, 1961, Ser. No. 147,147 9 Claims. (Cl. 149-37) The present invention relates to new and improved compositions for delay fuse powders of the type which comprise a mixture of inorganic oxidizing and reducing agents.

Delay detonators which are commonly commercially available generally consist of a tubular metal shell having one closed end, a base explosive charge, for example, pentaerythritol tetranitrate, positioned in the closed end, a primer charge or charges, for example, mannitol hexanitrate or diazodinitrophenol, positioned atop and in firing relation to the base charge, a delay element consisting of an incombustible tube containing a charge of delay fuse composition, positioned in firing relation to the topmost primer charge, an ignition means, for example, an electric match, mounted in firing position to the delay element, and electric wires adapted to connect the ignition means to a source of electrical energy extending from the ignition means through a plug or seal positioned in the open end of the detonator shell.

Prior to the advent of short period delay blasting techniques, blasting operations frequently employed delay detonators having delay times in increments of about one half second each. The advent of short period delay blasting techniques, wherein the delay intervals used start as low as 8 milliseconds and generally have intervals between successive delay periods in increments of from about 25 to about 125 milliseconds, brought a demand for delay fuse compositions which have a fast, reliable, and highly accurate propagation speed and which can provide short, accurate delay intervals when used in delay detonators. Hereinafter, a delay detonator having such shortened delay times will be referred to in the present application as a short period delay detonator.

In addition to the criteria which a delay fuse composition has to fulfill to be acceptable for use in a regular delay detonator, such as good reliability, good stability, easy ignition and easy and safe manufacture, a delay composition suited for use in short period delay detonators must have a fast and highly accurate propagation speed which is not substantially altered by prolonged storage. It will be readily appreciated that the deviation, from a mean detonation time in a short period delay detonator composition must be very smallin order to sharply define the respective delay periods and minimize the overlapping of one delay period with another. In addition, it is desiried that the short period delay fuse composition have a sufficiently constant and fast burning speed that delay times may be accurately predicted during manufacture by measurement of the delay train length. It also is desired that the increments of powder making up the delay train length be of sufficient size to facilitate rapid quantity production with available equipment.

According to the present invention, a delay fuse com- I position is provided by an intimate mixture of finely divided zirconium-nickel alloy fuel and an oxidizing agent selected from the group consisting of red lead and potassium permanganate. A secondary fuel, for example silicon, may be utilized in admixture with the potassium permanganate. The zirconium-nickel alloy preferably contains between about 20 and about 80 percent by weight of zirconium. Preferably the compositions of the present invention contain from about 30 to about 85% by weight of zirconium-nickel alloy, and from 15 to about 70% by weight of a member selected from the group of red lead nited States Patent which are difficult to predict. The inclusion of less than about 15 or more than about 70% by weight of an oxidizing agent selected from the group consisting of red lead and potassium permanganate yields compositions which propagate burning at an undesirably low level.

A delay fuse composition of the present invention may be prepared by intimately blending the components in a finely divided form by any suitable blending procedure; suitable blending may be obtained by placing the components in a double cone blender and operating the blender for a period of about 16 hours. In order to obtain a delay fuse composition free from undesirable small particles which would make the composition difiicult to handle and which would be a hazard during later operations such as charging the composition into the delay tubes, the blend is preferably pelleted to obtain a pellet, and the pelleted product granulated to obtain a granular product. The granulated product may then be screened to separate a powder having a grain size of between about that which will pass a 20 mesh U.S.S. screen and about that which can be held on a mesh U.S.S. screen. A suitable pellet may be obtained by placing the blended mixture in a pelleting press and compacting the mixture under a pressure of at least about 2,000 pounds per square inch; The separated product from the granulating step which is free of undesirable small particles and has a relatively uniform size is eminently suited to be packed into delay tubes to form charged delay elements.

A delay element may be produced by packing a charge of delay fuse composition of the present invention into a tubular member, preferably of a non-sparking metal, for example, aluminum, lead, copper or brass, which is of'a size to be received and function as a component in a delay detonator. Generally, the delay tubes found in commercially available delay electric detonators have an inside diameter between about 0.08 and about 0.14 inch. The delay composition is pressed under high pressure in the tube by means of a press pin or other suitable means. Utilization of pressures in the order of about 30,000 poundsper square inch is quite customary. A 25 millisecond increment of the delay powder of the present invention whenpressed in a delay tube will occupy a height of at least about 0.04 inch. By varying the length of the charge in such a delay tube a delay element may be produced having any desired delay time.

The invention may be more specifically illustrated by reference to the following table which shows the results of a series of tests conducted with delay fuse compositions of the present invention. The fuse compositions were comabout that which will be held on a 100 mesh U.S.S. screen.

In each test the delay fuse composition was packed into a brass delay tube having a 0.132 inch bore and having a inch length. The granular delay fuse composition was packed into the tube in small increments. Each in crement was placed in the tube separately and compacted under about 30,000 pounds per square inch. After com- In a preferred form of the invention the ingredients 3 pacting each increment had a height of between about .06 and about .07 inch. Nine increments were usually required to be added and compacted to completely fill the delay tube and form a charged delay element. The charged delay elements were then assembled along with the other detonator components into short period delay electric detonators. The assembled short period delay electric detonators were then apportioned into groups for testing. The delay time of some of the detonators in each group was determined immediately. The delay time of the remaining detonators in the group was determined after an accelerated storage test wherein the detonators were stored at a temperature of 50 C. for periods of from 1 to 6 months. In all of the tests the delay times were determined by utilizing a high speed timer to measure the time elapsing between application of the current to the detonator and the detonation of the detonator. Table I shows the results of a series of such tests. For each example, Table I shows: (1) the composition of the delay fuse composition; (2) the length of storage; (3) the mean delay time; (4) the scatter, i.e., the difference between the minimum and maximum delay times of the detonators in the group tested, and (5) the number of detonators tested. To illustrate the table, Example 1 shows the results of five tests that were conducted with detonators having a delay fuse composition compounded of an alloy of zirconium and nickel containing 30% by weight zirconium and red lead in equal amounts by weight. The mean delay time found for the five detonators was 193 milliseconds and the scatter was 56 milliseconds. Examples 2 through 4 show the results of a series of accelerated aging tests wherein short period delay detonators containing a delay fuse powder having the composition of Example 1 was stored at a temperature of 50 C.

Table II shows the results of a series of timing tests which were conducted using short period delay detonators which included delay fuse compositions of the present invention. The detonators were assembled from conventional delay detonator components which included in firing order; an ignition means, a charged delay element, a primer charge, and a base charge. The delay elements in each detonator were charged with delay fuse compositions compounded in accordance with the present invention compacted into the tube under a pressure of about 30,000 pounds per square inch. The desired delay times shown in Table II are normal delay intervals utilized in short period delay electric detonators. The expected burning speed of the present delay compositions when compacted into delay tubes was determined by measuring the time required for a known length of compacted fuse composition to burn, for example, such determination may easily be made from data similar to that shown in Table I. The length of delay fuse composition compacted into the delay tubes of the detonators tested was varied in accord to the expected burning speed to give the desired delay interval. The actual delay intervai was determined by connecting the leg wires to a source of electrical current and measuring the time elapsing between the time the current is applied and the time the detonator detonates by means of a high speed timer. To illustrate, Example 1 of the table shows the results of a series of tests conducted with individual delay detonators containing a delay composition of 65% by weight of a zirconium-nickel alloy containing 30% by weight of zirconium and by weight of potassium permanganate. The desired delay time was 45 milliseconds. The actual delay time in eleven tests averaged milliseconds with a scatter of 11 milliseconds.

T able II Delay Composition (Percent By Desired Fuse Actual Delay Weight) Delay Train Timcfln Milli- Number Example No. Time Length seconds) of Deto- (In (in nators M illl- Inches) Tested Zr/Ni Ph O KMnO Si seconds) Mean Scatter 65 0.109 40 ll 1 65 225 0. 547 225 1'1 11 65 675 l. 631 689 43 ll 120 0. 328 127 45 '1 50 200 0. 547 193 15 5 45 0.109 45 8 5 00 225 0.547 224 31 5 for periods of one, two and seven months. Examples 2 Although the present invention nas been described in through 14 were carried out in a similar manner to that described for Example 1. The Zr/Ni alloy shown in Examples 1 through 14 contained 30% by weight zirconium. The Zr/Ni alloy shown in Examples 15 through 17 contained by weight zirconium.

detaii in terms of fuse compositions for blasting detonators, it will be understood that the present compositions are eminently suited to use in delay trains in other types of devices in which accurate timing is required, for a example, in the delay fuses used in rockets, artillery shells,

grenades, and other ordnance and pyrotechnical devices. The term consisting essentially of" as used in the claims, includes compositions containing the named ingredients and other ingredients which do not deleteriously alfect the compositions for the purposes stated in the specification.

What is claimed is: 1. A delay fuse composition consisting essentially of an intimate mixture of a finely divided alloy of zirconium and nickel containing between about 20 and about 80% by weight of zirconium, and an oxidizing agent selected from the group consisting of red lead, and potassium permanganate said alloy being present in an amount of from about 30 to about 85 by weight of the composition. 2. A delay fuse composition consisting essentially of an intimate mixture of a finely divided red lead and alloy of zirconium and nickel containing between about 20 and about 80% by weight of zirconium, said alloy being present in an amount of from about 30 to about 85% by weight of the composition. 3. A delay fuse composition consisting essentially of an intimate mixture of a finely divided potassium permanganate and alloy of zirconium and nickel containing between about 20 and about 80% by weight of zirconium, said alloy being present in an amount of from about 30 to about 85% by weight of the composition. 4. A delay fuse composition consisting essentially of an intimate mixture of a finely divided alloy of zirconium and nickel containing between about 20 and about 80% by weight of zirconium a mixture of potassium permanganate and silicon said alloy being present in an amount of from about 30 to about 85% by weight of the composition. 5. A delay fuse composition consisting essentially of an intimate mixture of a finely divided fuel consisting of an alloy of zirconium and nickel containing between about 30 and about by weight of zirconium.

and an oxidizing agent selected from the group consisting of red lead, and

potassium permanganate said alloy being present in an amount of from about 30 to about by weight of the composition.

6. The composition of claim 5 wherein the oxidizing agent is red lead.

7. The composition of claim 5 wherein the oxidizing agent is potassium permanganate.

8. The composition of claim 5 wherein the composition contains a mixture of potassium permanganate and a secondary fuel of silicon,

said mixture containing between about 2 and about 5% by weight of silicon.

9. A delay fuse composition consisting essentially of an intimate mixture of finely divided alloy of zirconium and nickel,

and an oxidizing agent selected from the group consisting of red lead, and potassium permanganate,

said alloy of zirconium and nickel containing from about 30 to about 70% by weight of zirconium,

said oxidizing agent present in an amount ranging from about 15 to about 70% by weight of the composition, and

said alloy of zirconium and nickel present in an amount ranging from about 30 to about 85 by weight of the composition.

References Cited in the file of this patent UNITED STATES PATENTS 2,457,860 Bennett et al. Jan. 4, 1949 2,775,514 Wainer Mar. 26, 1953 2,992,086 Porter July 11, 1961 FOREIGN PATENTS 555,360 Canada Apr. 1, 1958 

1. A DELAY FUSE COMPOSITION CONSISTING ESSENTIALLY OF AN INTIMATE MIXTURE OF A FINELY DIVIDED ALLOY OF ZIRCONIUM AND NICKEL CONTAINING BETWEEN ABOUT 20 AND ABOUT 80% BY WEIGHT OF ZIRCONIUM, AND AN OXIDIZING AGENT SELECTED FROM THE GROUP CONSISTING OF RED LEAD, AND POTASSIUM PERMANGANATE SAID ALLOY BEING PRESENT IN AN AMOUNT OF FROM ABOUT 30 TO ABOUT 85% BY WEIGHT OF THE COMPOSITION. 